We use the present continuous to talk about things that we have already arranged to do in the future.

I've got my ticket. I'm leaving on Thursday.

I'm seeing Julie at 5 and then I'm having dinner with Simon.

He's picking me up at the airport.

The company is giving everyone a bonus for Christmas.

In many situations when we talk about future plans we can use either the present continuous or the 'going to' future. However, when we use the present continuous, there is more of a suggestion that an arrangement has already been made.

I'm going to see him./I'm seeing him.

I'm going to do it./I'm doing it.

We use the present simple to talk about events in the future which are 'timetabled'. We can also use the present continuous to talk about these.